Healthy ecosystems play an essential role in increasing the resilience of people to climate change. Climate change, however, can damage the ability of ecosystems to provide life-supporting services and to protect society from climate-related stressors. Adaptation to climate change therefore needs to strengthen the resilience of both communities and ecosystems. Ecosystem-based adaptation (EbA) – the use of biodiversity and ecosystem services to adapt to the adverse effects of climate change – provides such adaptation solutions. EbA initiatives also contribute to climate change mitigation by reducing net emissions from ecosystem degradation and by enhancing carbon sequestration. Countries should consider EbA in their approach to adaptation, including in national adaptation plans. EbA has demonstrated potential to increase social and ecological resilience to climate change and adaptive capacity in the long term and in an economically viable way. The evidence of the effectiveness and economic viability of EbA, although largely anecdotal and project-derived, is promising. Quality data and tools are essential for determining the economic viability of EbA measures. Institutional arrangements, finance and capacity-building also play a critical role in ensuring the effectiveness of EbA. This synthesis report was prepared under the Nairobi work programme on impacts, vulnerability and adaptation to climate change in collaboration with members of Friends of EbA. Information in 45 submissions served as primary inputs.